The present invention is in the field of fuser stations for image forming machines. More specifically this invention relates to the skive plate assembly for aiding receiver sheet removal from a roller in a fuser in an electrographic process.
An image-forming machine transfers images onto a receiving sheet. This is done by selectively charging and then optically exposing a photoconductor to form an electrostatic latent image on the surface. Toner is deposited onto the photoconductor surface. The toner is charged, thus adhering to the photoconductor surface in areas corresponding to the electrostatic latent image. This pattern of toner is then transferred to the receiving sheet at a transfer station. The transfer station charges the medium to an opposing voltage, so that the toner on the photoconductor is attracted to the receiving sheet as it is placed in proximity to the photoconductor.
The transferred toner is not permanently fixed to the medium at the transfer station, however. Conventional electrographic printers have a fixing, or fusing, station located downstream from the transfer station, at which the transferred toner pattern is fused to the medium. Conventional fusing stations apply heat and pressure to fuse the transferred toner to the medium, after which it travels to a finishing station in the printer for collating, sorting, stapling or other binding, and other finishing operations.
A fuser station typically has a fuser roller, a pressure roller, and upper and lower skive assemblies. The fuser and pressure rollers are disposed to form a nip, or pinch region. The receiving sheet enters the nip to have the image fused onto it. The receiving sheet then exits the nip. The upper and lower skive assemblies are located adjacent to the exit of the nip to help remove and guide the receiving sheet away from the fusing and pressure rollers. The upper skive assembly typically has a number of skives, which are typically thin flexible elements extending towards the fusing roller to help strip the receiving sheet from the roller. A deflector plate is also used to help guide the receiving sheet into a decurler nip.
There are several problems associated with the previous designs. One such problem is “stubbing” of the skive plate on the roller, which can damage the roller. Another problem is condensation of water on the surface of the upper skive assembly. This is caused by water driven out of the receiver sheet by the high temperature of the fusing roller. This condensation forms droplets that may then drip onto a receiver sheet causing a visual defect.
To reduce the problem of condensation forming on the upper skive assembly, U.S. Pat. No. 6,564,030 by Baughman et al, which is hereby incorporated by reference, discloses a vented deflector plate. While this does reduce condensation considerably, heavier weight and larger size papers produce more condensation that is not completely dissipated with this design.
A skive plate assembly is desired which would reduce condensation even for larger and/or heavier weight papers, and which would not stub the roller.